The specific hypothesis to be tested in this proposal is the expression and activity of specific metabolizing enzymes CYP1A2, CYPC19, CYC2D6, CYP2E1 and CYP3A4 are subject to inhibition during IFN alfa-2b therapy, thereby predisposed to development of drug toxicity secondary to other agents administered for the management of symptoms associated with IFN therapy and primarily associated with the modulation of P450 metabolism of endogenous hormonal mediators directly influenced by IFN alfa-2b therapy.